<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>
<body>
  <script>
    function getBook(res) {
      console.log('得到请求结果', res);
    }
  </script>
  <script src="http://localhost:3000/api/getBook"></script>
  <script>
  var obj = {
    a : 1
   }//console.log 可能是异步 惰性的
   console.log(obj);
   console.log(obj.b);
   setTimeout(() => {
     obj.b = 123
   }, 10);
  </script>
</body>
</html>
